It is frequently desired to treat substrate surfaces during fabrication of semiconductive material wafers. Exemplary processes include procedures whereby surfaces of semiconductor substrates are cleaned and/or polished. To aid in interpretation of the claims that follow, the terms “semiconductor substrate” and “semiconductive substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. An exemplary semiconductive substrate is a wafer of monocrystalline silicon.
Among the methods of polishing a semiconductive material surface is chemical-mechanical polishing. Chemical-mechanical polishing is accomplished by providing a slurry of liquid and solid particulates over a wafer and mechanically abrading the wafer surface with the slurry. (The liquid can comprise, for example, an aqueous solution having ammonium ions therein, and the solid particulates can comprise, for example, silicon slurry particulates and/or cesium slurry particulates.) The mechanical abrasion can be accomplished by providing a polishing pad above the wafer surface and spinning one or both of the wafer and the pad to cause the wafer surface to be moved relative to the polishing pad. A problem that can occur during polishing of a wafer surface is in removal of the particulates from over the surface at the termination of the polishing process. Particulates that are not removed from over the wafer can cause damage to electrical devices formed over the wafer.
Several procedures have been developed to assist in cleaning particulates from a wafer surface. Among the procedures is to flush a liquid over the wafer surface while mechanically agitating the liquid with a cleaning member. Such cleaning member can comprise, for example, a brush or a polishing pad. The agitation of the liquid can help to dislodge particles from the wafer surface. Another method which has been utilized to clean a wafer surface is to project solid particles against the wafer surface. In one application, solid particles of carbon dioxide (CO2) are ejected against a semiconductive material surface to dislodge particles from the surface. An advantage of utilizing solid CO2 is that the material can be sublimed from the semiconductive material surface to enable easy removal of the material.
It would be desirable to develop alternative methods for cleaning and/or polishing substrates. It would be particularly desirable to develop alternative methods for polishing and/or cleaning semiconductive material substrates, such as, for example, monocrystalline silicon wafers.